Among the reservoir characterization technologies devoted to oilfields, complex permittivity measurements can provide information on the water saturation and the cementation factor of the rock formation in the vicinity of the borehole. Complex permittivity can be obtained from measurements made using wire line tools. For example, see tools such as The Schlumberger Electromagnetic Propagation Tool or The Schlumberger Dielectric Scanner tool working at various frequencies. There are three main features in rock systems that are important for understanding the broadband dielectric response: the rock solid polarization, fluid polarization, and rock-fluids interaction in the polarization process. In addition, in certain circumstances the fluid-fluid interfacial polarization can provide further information.
Tools such as Schlumberger's Dielectric Scanner tool measures the characteristics of propagation of travelling electromagnetic waves between emitting and receiving antennae. The dielectric permittivity and the conductivity of the geological formation at various frequencies are deduced from these data by inversion methods. From these physical parameters, reservoir properties such as cementation factor and water saturation can be estimated by way of dielectric “mixing” laws (reflecting the effect of each component in the wave propagation). As the dielectric permittivity values of the matrix and the fluids are separately entered in the mixing law, they all should be accurately known in order to reliably estimate the reservoir properties. The simplest mixing law necessary for the interpretation of the complex permittivity measurements in oil reservoirs is a volumetric distribution of the effect on the complex wave number of the electromagnetic propagating wave; the law is called the CRIM law (reputed to be valid at frequencies around and greater than 1 MHz):√{square root over (∈*)}=Swφ√{square root over (∈w*)}+(1−Sw)φ√{square root over (∈oi)}+(1−φ)√{square root over (∈rk)}Where:    ∈*=∈+jσ/ω∈0 Complex relative permittivity as measured by the tool;    ∈ is the real part of the complex permittivity, generally called “dielectric constant” or relative permittivity;    σ is the conductivity (S/m),    ω=2πf the angular frequency of the signal, where f is the Hertzian frequency;    ∈0 the dielectric permittivity of vacuum;    Sw Water saturation of offered volume, (1−Sw) is the oil saturation;    φ Rock porosity (volume fraction of void volume);    (1−φ) is the rock matrix volume;    ∈w* the water complex permittivity depends on temperature and salinity, which can be inferred if the brine is known;    ∈oi Oil dielectric constant (real, since oil conductivity is generally very low); and    ∈rk Matrix dielectric constant (real, since rock conductivity is generally very low).
Note that the matrix dielectric constant (real part of permittivity) can vary over a relatively large range (from 3 to 10 for instance). The water dielectric constant is in the range 50-100 and salinity can be assessed by various means, the conductivity of the medium being largely dependent on the conductivity of the water.
There is a need to obtain the relative dielectric constant of the rock (the real part of the permittivity) since it represents an offset in the measured data that has to be inferred by an independent means. A second input is the irreducible water saturation content of the cuttings.
The matrix dielectric constant from drilling cuttings from the same formation would provide this very important information for the dielectric measurement interpretation. Note that more complex mixture laws exist but all are based on the a priori knowledge of √{square root over (∈rk)}.
Various techniques for measurement of drilling cuttings have been discussed. For instance: Santarelli, Marsala, Brignoli, Rossi, N. Bona from AGIP in an SPE paper (36851), have reviewed advantages and disadvantages of formation evaluation based on measurements on cuttings. After drying the cuttings the porosity can be estimated by weighing the cuttings in a given volume and measure the air volume, and the sample mass.
In SPE/ISRM 47202 the same authors present a compact apparatus to measure low and very low permeability on cuttings in a cell with a pressure pulse excitation.
In an SPE paper (77563) a contingent method to measure permeability on cuttings is presented by IFP and IMFT (“Lenormand” school). The method is based on the injection of an oil into the cuttings placed in a chamber. When the oil enters the cuttings pores it expels Helium initially saturating the cuttings, the volume versus time of helium produced provides information on the cuttings permeability.
In an IADC/SPE 112687 paper “Automatic Measurement of Drilling Fluid and Drill Cuttings Properties”, the authors present a complex set up measuring among various parameters density, pH, H2S content, liquid particle size distribution, mud solids or raman spectroscopy.